Placozoa
Sign in to savePlacozoa ( ; ) is a phylum of free-living (non-parasitic) marine invertebrates. They are blob-like animals composed of aggregations of cells. Moving in water by ciliary motion, eating food by engulfment, and reproducing by fission or budding, placozoans are described as "the simplest animals on Earth". Structural and molecular analyses have supported them as among the most basal animals, thus constituting a primitive metazoan phylum.
AI overview
Placozoans are simple, blob-like marine animals composed of loosely organized cells that move through water using tiny hair-like structures and eat by engulfing food particles. They are considered among the most primitive animals on Earth, making them scientifically valuable for understanding how complex life evolved from simpler forms.
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Article
17 sectionsContents
- History
- Biology
- Anatomy
- Proto-nervous system
- Reproduction
- Endosymbionts
- Evolution and population dynamics
- Distribution
- Internal phylogeny
- Evolutionary relationships
- Functional-morphology hypothesis: Sister to Porifera and Eumetazoa
- Epitheliozoa hypothesis: Sister to Eumetazoa
- Eumetazoa/ParaHoxozoa hypotheses
- Sister to Planulozoa
- Sister to Cnidaria
- References
- External links
Placozoa ( ; ) is a phylum of free-living (non-parasitic) marine invertebrates. They are blob-like animals composed of aggregations of cells. Moving in water by ciliary motion, eating food by engulfment, and reproducing by fission or budding, placozoans are described as "the simplest animals on Earth". Structural and molecular analyses have supported them as among the most basal animals, thus constituting a primitive metazoan phylum.
The first known placozoan, Trichoplax adhaerens, was discovered in 1883 by the German zoologist Franz Eilhard Schulze (1840–1921). Recognizing its distinctive characteristics, the German zoologist Karl Gottlieb Grell (1912–1994) erected a new phylum, Placozoa, for it in 1971. Remaining a monotypic phylum for over a century, new species began to be added in 2018. So far, three other extant species have been described, in two distinct classes: Uniplacotomia (Hoilungia hongkongensis in 2018 and Cladtertia collaboinventa in 2022) and Polyplacotomia (Polyplacotoma mediterranea, the most basal, in 2019). A single putative fossil species is known, the Middle Triassic Maculicorpus microbialis.